Projector type headlamp of maximized light collecting efficiency

Abstract

An improved light collecting efficiency in a projector type automotive headlamp is achieved by including a curved mirror to re-direct light otherwise absorbed by a rear surface of the blocking cut-off shield in “low beam” operating mode of the headlamp. When the shield is moved to a second non-blocking position, a mirror segment conforms to the curved surface of the substantially ellipsoidal reflector to maximize lumen output in “high beam” operating mode of the headlamp. In addition, auxiliary mirror segments may be used to provide a more complete substantially ellipsoidal reflector configuration that maximizes the light collection efficiency. Preferably, the cap holder is purposefully offset in order to position the centerline of the bowed arc of the arc discharge light source in alignment with the optical axis of the optical system in order to maximize light collection efficiency.

Description

BACKGROUND OF THE DISCLOSURE[0001]This disclosure relates to a vehicle headlamp system, and more particularly to a headlamp system that employs a compact high intensity discharge lamp having at least two different lighting functions or modes (e.g., “high beam” and “low beam” modes) integrated into a single headlamp assembly. Selected aspects of this disclosure may also find application in related headlamp arrangements.[0002]Light collection efficiency of state of the art ellipsoidal projector modules of a projector-type automotive headlamp is moderate. Limitations associated with the light collection efficiency are basically driven by light absorption by the cut-off shield inserted into the module to block unwanted light rays when operated in “low beam” mode. The unwanted light rays in this mode are those that would otherwise be directed by the headlamp toward the eyes of an oncoming driver approaching the vehicle from the opposite direction. The cut-off shield defines a sharp light...

AI Technical Summary

Benefits of technology

[0015]By virtue of increased light collection efficiency, the total lumen output, road illuminance levels and projected beam angle of the projector type automotive headlamp can be increased using teachings of the present disclosure.

[0016]Another benefit is enhanced visibility on the road, or the ability to use a light source with a lower power consumption which, in turn, can lead to better fuel efficiency of a vehicle.

[0017]Still another advantage relates to enhancing light collection efficiency by the use of auxiliary mirrors and mirror segments rather than altering the overall dimensions of the projector module.

Problems solved by technology

Unfortunately, this proposed solution also has drawbacks.

For example, the small surface area of the projector lens means higher surface brightness, which can cause discomfort glare to oncoming drivers.

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